/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.common.util;

import java.util.Collection;
import java.util.Random;
import java.util.logging.Logger;

import static net.sf.freecol.common.util.RandomUtils.*;


/**
 * A class to provide flat and weighted random selection from a collection.
 */
public class RandomChoice< T >
{

    private final int probability;
    private final T object;


    public RandomChoice( T object, int probability )
    {
        this.probability = probability;
        this.object = object;
    }

    public int getProbability( )
    {
        return probability;
    }

    public T getObject( )
    {
        return object;
    }


    private static < T > T select( Collection< RandomChoice< T > > input,
                                   int probability )
    {
        if ( input.isEmpty( ) ) return null;

        int total = 0;
        for ( RandomChoice< T > choice : input )
        {
            total += choice.getProbability( );
            if ( probability < total ) return choice.getObject( );
        }
        return input.iterator( ).next( ).getObject( );
    }

    public static < T > int getTotalProbability( Collection< RandomChoice< T > > input )
    {
        return input.stream( ).mapToInt( c -> c.getProbability( ) ).sum( );
    }

    public static < T > T getWeightedRandom( Logger logger, String logMe,
                                             Collection< RandomChoice< T > > input,
                                             Random random )
    {
        int n;
        return ( input == null || input.isEmpty( )
                || ( n = getTotalProbability( input ) ) <= 0 ) ? null
                : ( input.size( ) == 1 ) ? input.iterator( ).next( ).getObject( )
                : select( input, randomInt( logger, logMe, random, n ) );
    }
}
